用简便方法
1。5/7X83+1/7X85
2. 13/23X12+13X11/23
3. 275/277X278
4. 55 1/3X3/5-42 2/3X3/8+36 3/4X4/7
用简便方法
1。5/7X83+1/7X85
2. 13/23X12+13X11/23
3. 275/277X278
4. 55 1/3X3/5-42 2/3X3/8+36 3/4X4/7
1:5/7X83+1/7X85=1/7X415+1/7X85=1/7X(85+415)=1/7X500=500/7
2:13/23X12+13X11/23=1/23X156+1/23X143=1/23X(156+143)=1/23X300-1/23=299/23
4:55 1/3X3/5-42 2/3X3/8+36 3/4X4/7=55/3X3/5-28X3/8+27X4/7=11-84/8+108/7=11-588/56+864/56=892/56